For patients suffering from bedsores (decubitus), risk of bedsores or burns, mattresses which provide pressure relief have long been known and many have been placed on the market and put in use. A first type of such mattresses is exemplified by the Pegasus Airwave (registered trade mark) mattress, which has a double-layer array of cells in the form of tubes which are divided into groups which are sequentially inflated and deflated in a predetermined cycle (see GB-A-1595417). The tubes are of air-impermeable material, and are deflated by venting to atmosphere. Alternatively, in accordance with GB-A-2312835, the tubes are deflated by connection to a suction pump or pumps. It is an advantage of the Pegasus Renaissance mattress that it permits the use of an overlay or cover between the array of tubes and the patient, which has merits in hygiene and infection control, as well as appearance and comfort. A particular form of cover, which minimizes risk of interface pressure retention, is described in patent application EP-A-827705 of Pegasus.
It is preferable for the mattress to have means for preventing a patient from rolling off the mattress. Ideally the means is provided by portions of the mattress itself, e.g. by formations provided along both sides of the mattress.
Previously, this has been achieved using inflatable cells, known as side formers, located at sides of the mattress, which remain inflated continuously during inflation and deflation cycles of the groups of tubes. However, these side formers need an air supply which is independent of the alternating pressure air supply to the tubes. This causes manufacturing difficulties, and increases costs.
Alternative prior art side formations are e.g. solid side formations, formed of e.g. foam material. However, during Cardiopulmonary Resuscitation (CPR) procedures etc., where unobstructed access to a patient lying on the mattress is required, it is desirable for the mattress to be made flat. Unlike inflatable side formations, which can be deflated, solid side formations remain protruded from the mattress always.